Iron ore frequently contains a considerable amount of silicate. The presence of silicate has been found to have a negative effect on the quality of the iron and complicates the process for the production of iron. It is therefore essential that the silicate content of the enriched iron mineral can be reduced to a considerable extent, for instance, to a level below 1% by weight.
A frequent method of reducing the silicate content is to carry out inverted froth flotation, the silicate being enriched in the flotate and the iron ore in the bottom fraction. Such froth flotations are disclosed in, inter alia, U.S. Pat. No. 4,732,667, which suggests removal of silicate from iron ore by carrying out froth flotation by using a collecting agent, which contains a primary amine, for instance, an ether amine, in combination with a nitrogen-containing compound which also has an anionic group.
Patent Specification WO 93/06935 discloses the use of at least one ether amine in combination with at least one anionic compound or collecting agent, in froth flotation of silicate-containing iron ore.
Other examples of froth flotation of silicate-containing iron ores are described in U.S. Pat. Nos. 4,319,987 and 4,168,227, in which ether monoamines and mixtures of an ether amine and an amino-1-alkane are used as collecting agents.
CA 1 100 239 discloses the use of monoamines or diamines dispersed with an emulsifying agent as a collector in froth flotation without causing a considerable corrosion of apparatus utilized in the process. A general tendency when applying these froth flotation processes is that the enriched iron mineral has a low silicate content combined with a low iron yield, or a high iron yield and a comparatively high silicate content.
The aim of the present invention is to develop a froth flotation process which results in a high yield of the iron mineral as well as a low silicate content, i.e. develop a more selective flotation process.